Consumption of phytochemical-rich fruits and vegetables is associated with a lower risk of oral cancer and protection against oxidative stress-mediated damage from reactive oxygen species (ROS). It is proposed that antioxidant components in black raspberries (BRB) can “scavenge” ROS and diminish oxidative burden in the oral cavity. Therefore, we tested the hypothesis that a long-term, low-dose dietary administration of BRB to a population of disease-free oral cancer survivors is both (i) achievable and (ii) will result in the attenuation of oxidative DNA damage.
Participants were assigned to consume 0, 4, or 8 grams of BRB daily for 6 months and provided self-report logbooks of adherence. Mass spectrometry of participant urine was used to identify biomarkers of adherence: dimethyl ellagic acid (DMEA) and urolithins. ELISA analysis of urine was used to measure 8-hydroxy-2’-deoxyguanosine (8-OHdG). Nanostring technology was employed to interrogate gene expression pathways associated with oxidative stress and DNA damage. Furthermore, a logistic regression model was developed to determine factors associated with willingness to participate and continue with study once enrolled.
112 participants were enrolled to a BRB or control regimen. Mean self-reported adherence to the study regimen for those returning logbooks was 88% at 10 & 20 weeks (CI: 83.87-92.65 & 85.81-91.89, respectively). MS/MS measurements of DMEA was 10-fold higher in BRB treated participants (p<0.0001 and 0.0015) at 10 and 20 weeks and urolithins were significantly higher in BRB participant urine at 10 weeks (p-0.0245). ELISA measurements of 8-OHdG in urine at 10 and 20 weeks was significantly decreased (p=0.0183 and p=0.0102) in BRB participants. Gene analysis of mucosal samples demonstrated significant down-regulation of NFKB2 (p=0.0282), NRF2 (0.0507), NQO1 (p=0.0011), GCLC (p=0.0468), and up-regulation of KEAP1 (p=0.0194) in BRB participants at 10 weeks.
Predictive modeling revealed barriers associated with participation in the study which included: current smoker vs. never/past (OR: 7.85/4.86, p<0.0001/p=0.0003), physician engagement (OR: 5.71, p=0.0005), increasing age (p<0.0014), and adjuvant treatment (chemotherapy and/or radiation vs. none) (OR: 5.91 and 3.46, p<0.0001 and p=0.001). Once enrolled on study, those having the least travel distance (p<0.003), and government (OR: 3.96 & 7.04; p<0.02) or private insurance (OR: 5.1; p<0.01) vs. no insurance were more likely to complete. Additionally, past (OR: 3.85; p<0.02) and current smokers/tobacco users (OR: 3.82; p<0.03) continuing on after week 10 were more likely to complete than never smokers.
This research demonstrates that a food-based prevention strategy, utilizing BRB in oral cancer survivors, is safe and feasible. Participants completing the study maintained an outstanding level of adherence with humoral biomarkers (DMEA, urolithins) serving as objective means of validation. Issues influencing the initial decision of patients to enroll and continue on once enrolled were identified. Long-term, low-dose administration of BRB effectively decreased urinary levels of 8-OHdG, an established biomarker of DNA damage, and significantly regulated genes/pathways associated with inflammation, carcinogen metabolism, and oxidative stress, all of which are associated with development of oral cancer. Results from this study provide evidence that administration of BRB may offer loco-regional and systemic benefits with very low potential for adverse effects.
Committee: Christopher Weghorst, PhD (Advisor); Steven Clinton, MD, PhD (Committee Member); Dennis Pearl, PhD (Committee Member); Sun Qingua, MD, PhD (Committee Member); Randi Love, PhD (Committee Member)